GMAT Practice Question Set #13 (Question 37-39)

Journalist: The end of the Triassic, the geologic period that extended from about 250 to 200 million years ago, has traditionally been blamed on volcanic eruptions that went on for 600,000 years. However, a researcher has recently suggested that these eruptions were only an indirect cause. By analyzing the isotopic composiion of hydrocarbon molecules from plant waxes from the period, he discovered what looks like a spike in the amount of nonbiological carbon in the atmosphere, lasting between 10,000 and 20,000 years. The researcher believes that the release of methane -- a carbon-containing greenhouse gas much stronger than carbon dioxide -- stored at the bottom of the ocean was the direct cause of the end of the Triassic.

The journalist suggests that a certain causal sequence may have brought about the end of the Triassic period. Identify in the table the sequence of cause and effect most strongly suggested by the journalist to have resulted in the end of the Triassic. Make only two selections, one per column.

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